JP2000038512A - Semiconductive resin composition and semiconductive roller by use thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a variation in electric resistance even in the case of a monolayer structure by incorporating a carbon black having not more than specific values of a DBP oil-absorbing amount and iodine-adsorptive amount as a conductivity-imparting agent. SOLUTION: The carbon black used as a conductivity-giving agent has a DBP oil-absorbing amount of not more than 100 mL/100 g and an iodine- absorptive amount of not more than 25 mg/g. As a semiconductive and elastic layer of a resin composition, a reaction product of a curing composition comprising: a polymer composed of an oxyalkylene unit or a saturated hydrocarbon as a repeat unit to constitute a main chain unit, containing at least one alkenyl group in a molecule; a curing agent containing at least two hydrosilyl groups in the molecule; and a hydrosilyl catalyst, as main components, is preferably used. A phosphate compound as a conductive auxiliary may be added to this composition in an amount preferably of 2-30 wt.% relative to the carbon black.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to a copying machine,
The present invention relates to a semiconductive resin composition used for a charging roller, a developing roller, and a transfer roller incorporated in an apparatus employing an electrophotographic method such as a printer or a facsimile receiving apparatus, and a semiconductive roller using the same.

[0002]

2. Description of the Related Art A charging roller, a developing roller, a transfer roller and the like used in an electrophotographic apparatus are required to be semiconductive. The semiconductivity in this case is, for example, DC1
Volume resistivity at the time of application of 00V is 10K (10 ⁴ ) Ωcm ~
It means that it is about 1 G (10 ⁹ ) Ωcm.

[0003]

From the viewpoint of cost, the most inexpensive semiconductive roller has a structure in which only a single semiconductive elastic layer is coated on a conductive support such as a metal shaft. is there. However, since it is difficult to control the semiconductivity with one layer, the semiconductive elastic layer is often provided with a relatively low resistance, and one or more resin layers are provided on the outer periphery thereof. However, in this case, the number of steps for manufacturing the roller increases, and the cost of the roller increases.

On the other hand, in a developing roller used in a non-magnetic non-contact developing device to which an AC voltage is applied, even if the developing roller has the above-mentioned multilayer structure (as is clear from an equivalent circuit of electric resistance and capacitance). (2) The electrical resistance of the elastic layer having rubber elasticity becomes important, and it cannot be dealt with simply by reducing the resistance.

[0005]

SUMMARY OF THE INVENTION The present invention aims at providing a composition having a small variation in electric resistance even if it has a single-layer structure (it can be applied to a developing roller whose surface is further coated). As a result of diligent studies, the inventors have focused on DBP lubrication as a measure of carbon black structure and iodine adsorption as a measure of particle size, and to fill relatively large amounts of low structure, large particle size carbon black. Is important for controlling the electric resistance uniformly in the semiconductive region, and when these carbon blacks are used, when the main chain is an oxyalkylene compound, the carbon has low viscosity, so It is easy to fill a large amount of black, and when the main chain is a saturated hydrocarbon unit, carbon black is often easily dispersed. By phthalic acid ester compound added 2 wt% to 30 wt% carbon black,
The present inventors have found that a phthalic acid ester compound is adsorbed on the surface of carbon black to improve dispersibility and act as a conductivity-imparting aid, thus completing the present invention. That is,
The present invention is a semiconductive resin composition, which comprises, as a conductivity-imparting agent, carbon black having a DBP oil absorption of 100 ml / 100 g or less and an iodine adsorption of 25 mg / g or less. Composition (Claim 1) The semiconductive resin composition has (A) at least one alkenyl group in a molecule,
A polymer in which a repeating unit constituting the main chain is an oxyalkylene unit or a saturated hydrocarbon unit. (B) a curing agent having two or more hydrosilyl groups in a molecule; and (C) a hydrosilylation catalyst. The semiconductive composition according to claim 1, wherein the phthalic acid ester compound is contained in an amount of 2% by weight to 3% by weight of the conductivity-imparting agent.
The semiconductive resin composition according to claim 1 or 2, wherein the molded product has a volume resistivity of 10 M (10 ⁷ ) Ωcm to 1.
G (10 ⁹ ) Ωcm.
The semiconductive resin composition according to any one of claims 3 to 6 (Claim 4) The semiconductive resin used in an electrophotographic method using the semiconductive resin composition according to any one of claims 1 to 4. A roller (Claim 5) has the content.

[0006] The DBP oil absorption referred to in the present invention is defined by JIS.
K6221 is an amount measured by the method A (spring tension B type) measured using an absorbometer specified in "Testing method for carbon black for rubber", and the iodine adsorption amount is also a measured amount based on JIS K6221.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the semiconductive resin composition of the present invention is mainly used for producing rollers used in electrophotographic copying machines or printers. DBP oil absorption of 100ml / 100g or less and iodine adsorption of 25mg /
Examples of the carbon black having a weight of g or less include Asahi # 15, Asahi # 15HS, Asahi # 50, and Asahi # 35 manufactured by Asahi Carbon Co., Ltd. More preferably DBP oil absorption 65ml / 10
0 g or less, iodine adsorption amount of 25 mg / g or less, most preferably DBP oil absorption of 50 ml / 100 g or less, iodine adsorption of 20 mg / g or less. Asahi # 15 has a DBP oil absorption of 40 ml / 100 g and iodine adsorption of Is about 14 mg / g, which is very preferable.

Next, the semiconductive resin composition of claim 2 will be described. As the semiconductive elastic layer, (A) a polymer containing at least one alkenyl group in a molecule, and a repeating unit constituting a main chain mainly consisting of an oxyalkylene unit or a saturated hydrocarbon unit; B) a curing agent containing at least two hydrosilyl groups in the molecule;
It is preferable to use a reaction product of the curable composition containing (C) a hydrosilylation catalyst and a main component. When the semiconductive elastic layer is composed of an oxyalkylene-based composition, the composition has a low viscosity before curing and a low hardness after curing, so that it is preferable from the viewpoint of workability, and the semiconductive elastic layer is saturated. When composed of a hydrocarbon-based composition, this composition has a low water absorption and is therefore preferable from the viewpoint of stability under a high humidity environment.

The polymer of the component (A) in the curable composition is a component which is cured by a hydrosilylation reaction with the component (B) and has at least one alkenyl group in the molecule. Occurs to become a polymer and harden. The number of alkenyl groups contained in the component (A) is required to be at least one from the viewpoint of performing a hydrosilylation reaction with the component (B), but from the viewpoint of rubber elasticity, in the case of a linear molecule, In the case of a molecule having two alkenyl groups at both ends and a branched molecule, it is preferable that two or more alkenyl groups are present at the molecular ends. (A)
The main repeating unit constituting the main chain of the component is an oxyalkylene unit or a saturated hydrocarbon unit.

In the case of a polymer in which the main repeating unit constituting the main chain is an oxyalkylene unit, the volume resistivity is 10 ⁸ to 10 ⁹ Ωcm only by adding a small amount of a conductivity-imparting agent.
Is preferable. Further, from the viewpoint of lowering the hardness of the cured product, an oxyalkylene-based polymer in which the repeating unit is an oxyalkylene unit, and more preferably an oxypropylene-based polymer in which the repeating unit is an oxypropylene unit.

Here, the oxyalkylene-based polymer refers to a polymer in which 30% or more, preferably 50% or more, of the units constituting the main chain are composed of oxyalkylene units. Examples of the unit include compounds derived from compounds having two or more active hydrogens, such as ethylene glycol, bisphenol compounds, glycerin, trimethylolpropane, and pentaerythritol, which are used as starting materials in the production of polymers. . In the case of an oxypropylene-based polymer, it may be a copolymer (including a graft polymer) with a unit composed of ethylene oxide, butylene oxide, or the like.

The molecular weight of the oxyalkylene polymer as the component (A) is from 500 to 50,000 in terms of number average molecular weight (Mn) from the viewpoint of improving the balance between reactivity and hardness reduction. Is 1,000-40,0
00 is preferred. In particular, the number average molecular weight is 5,0
Those having a value of 00 or more, more preferably those having a molecular weight of 5,000 to 40,000 are preferred. When the number average molecular weight is less than 500, it becomes difficult to obtain sufficient mechanical properties (rubber hardness, elongation) and the like when the curable composition is cured. On the other hand, if the number average molecular weight is too large, the molecular weight per alkenyl group contained in the molecule will be large, or the reactivity will decrease due to steric hindrance, so curing is often insufficient, Further, the viscosity tends to be too high and the processability tends to be poor.

Although the alkenyl group contained in the oxyalkylene polymer is not particularly limited, the following general formula (1): H ₂ C = C (R ¹ )-(1) (wherein R ¹ is a hydrogen atom or The alkenyl group represented by (methyl group) is particularly preferable in terms of excellent curability.

One of the features of the curable composition is that
In order to exhibit this characteristic, the number of alkenyl groups is preferably 2 or more at the molecular terminal, and the number of alkenyl groups becomes too large compared to the molecular weight of component (A). And it becomes difficult to obtain good rubber elasticity. In the case where the component (A) is a polymer in which the main repeating unit constituting the main chain is a saturated hydrocarbon-based unit, the polymer preferably has a low water absorption and a small environmental fluctuation of electric resistance. This polymer is also a component which is cured by a hydrosilylation reaction with the component (B), as in the case of the oxyalkylene polymer, and has at least one alkenyl group in the molecule. The component (A) is required to have at least one alkenyl group from the viewpoint of a hydrosilylation reaction with the component (B).
From the viewpoint of rubber elasticity, in the case of a linear molecule, two molecules are preferably present at both ends of the molecule, and in the case of a molecule having a branch, two or more molecules are preferably present at the molecular terminal.

Typical examples of the polymer in which the main repeating unit constituting the main chain is a saturated hydrocarbon-based unit include:
Examples include an isobutylene-based polymer, a hydrogenated isoprene-based polymer, and a hydrogenated butadiene-based polymer. These polymers may contain a repeating unit of another component such as a copolymer, but at least 50% of a saturated hydrocarbon-based unit may be contained.
As described above, it is important that the content is preferably 70% or more, more preferably 90% or more, so as not to impair the characteristic of the saturated hydrocarbon system having a low water absorption.

The molecular weight of the polymer of the component (A) in which the main repeating unit constituting the main chain is a saturated hydrocarbon-based unit is, for example, a number average molecular weight (M
n) about 500 to 50,000, and even 1,000
~ 15,000, and a liquid material having fluidity at room temperature is preferable from the viewpoint of processability. About the alkenyl group introduced into this saturated hydrocarbon polymer,
The same applies to the case of the oxyalkylene polymer.

Therefore, preferred specific examples of the polymer having at least one alkenyl group in the molecule and having a main repeating unit constituting a main chain of a saturated hydrocarbon, as component (A), include: A linear number average molecular weight (Mn) having two alkenyl groups at both ends is from 2,000 to 1
Examples thereof include a polyisobutylene-based, hydrogenated polybutadiene-based, and hydrogenated polyisoprene-based polymer having a molecular weight of 5,000 and an Mw / Mn of 1.1 to 1.2. Here, Mw indicates a weight average molecular weight.

The component (B) in the curable composition is not particularly limited as long as it is a compound having at least two hydrosilyl groups in the molecule, but the number of hydrosilyl groups contained in the molecule is too large. After curing, a large amount of hydrosilyl groups easily remain in the cured product and cause voids and cracks. Therefore, the number of hydrosilyl groups contained in the molecule is preferably 50 or less. Further, the number is preferably 2 to 30, more preferably 2 to 20, from the viewpoint of control of rubber elasticity and storage stability of the cured product. Further, in order to easily prevent foaming during curing, 20 Hereinafter, three or more are preferable in that hardening failure hardly occurs even when the hydrosilyl group is deactivated, and the most preferable range is 3 to 20.

In the present invention, the hydrosilyl group is substituted with 1
The term “having one” means having one H bonded to Si. In the case of SiH ₂ , it has two hydrosilyl groups, but the H bonded to Si is harder to bond to different Si. And also preferable from the viewpoint of rubber elasticity.
The molecular weight of the component (B) is determined based on the number average molecular weight (M
n) is preferably 30,000 or less, more preferably 20,000 or less, and particularly preferably 15,000 or less. Considering the reactivity and compatibility of the component (A), 300
It is preferably from 10,000 to 10,000.

Regarding the component (B), since the cohesive force of the component (A) is greater than the cohesive force of the component (B), the phenyl group-containing modification is important in terms of compatibility. Styrene-modified products are preferred from the viewpoint of compatibility with the components and availability, and α-methylstyrene-modified products are preferred from the viewpoint of storage stability. The hydrosilylation catalyst as the component (C) is not particularly limited as long as it can be used as a hydrosilylation catalyst. Platinum simple substance, solid platinum supported on simple substance such as alumina, chloroplatinic acid (including complex such as alcohol), various complexes of platinum, rhodium,
Chloride of metals such as ruthenium, iron, aluminum, titanium and the like can be mentioned. Among these, chloroplatinic acid, a platinum-olefin complex, and a platinum-vinylsiloxane complex are preferable from the viewpoint of catalytic activity. These catalysts may be used alone or in combination of two or more.

The ratio of the component (B) to the component (A) in the curable composition as described above is such that the hydrosilyl group in the component (B) is 0.2 per mole of the alkenyl group in the component (A). -5.0 mol, more preferably 0.4-2.5 mol, from the viewpoint of rubber elasticity. The amount of the component (C) used is 1 to 1 mole of the alkenyl group in the component (A).
It is preferably used in the range of 0 ^-1 to 10 ^-8 mol, more preferably 10 ^-1 to 10 ^-6 mol, particularly preferably 10 ^-3 to 10 ^-6 mol.
If the amount of component (C) is less than 10 ^-8 mol, the reaction does not proceed. On the other hand, hydrosilylation catalysts are generally expensive, corrosive, and have the property that a large amount of hydrogen gas is generated and the cured product foams.
It is preferred not to use more than 10 ^-1 mol.

The added amount of the conductivity-imparting agent is (A) to (C)
It is preferable that the content be 30% by weight or less based on the total amount of the components, since the rubber hardness is not increased. On the other hand, the amount is preferably 10% by weight or more from the viewpoint of obtaining a uniform resistance, and the amount to be added may be determined based on the balance between the required rubber hardness and the volume resistivity of the cured product. Further, in addition to the components described above, the curable composition may further contain a storage stability improver, for example, a compound having an aliphatic unsaturated bond, an organic phosphorus compound, an organic sulfur compound, a nitrogen-containing compound, or a tin-based compound. Compounds, organic peroxides and the like may be added. For example, for example,
Examples include, but are not limited to, benzothiazole, thiazole, dimethylmalate, dimethylacetylenecarboxylate, 2-pentenenitrile, 2,3-dichloropropene, quinoline, and the like. Among these, thiazole and dimethyl malate are particularly preferred from the viewpoint of achieving both pot life and rapid curing properties. The storage stability improvers may be used alone or in combination of two or more.

Further, a filler, a storage stabilizer, a plasticizer, an ultraviolet absorber, a lubricant, a pigment, and the like for improving processability and cost may be added to the curable composition. The semiconductive roller according to the present invention is a curable composition as described above,
In addition, an elastic material such as urethane rubber, chloroprene rubber, and EP rubber is cast into a mold having a conductive shaft made of a metal shaft such as SUS in the center, for example, injection molding, extrusion molding, and the like. A semiconductive elastic layer is formed around the shaft by heating and curing at an appropriate temperature and time. In this case, post-curing may be performed after semi-curing. If necessary, one or more other layers may be provided outside the semiconductive composition having rubber elasticity.

Next, the phthalate compound of claim 3 will be described. Dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate (DOP), diisooctyl phthalate, n-octyl phthalate, dicyclohexyl phthalate, butyl phthalate Benzyl, diisodecyl phthalate (DIDP) and the like. DOP and DIDP are preferred from the viewpoints of availability and bleedlessness. The amount used is 2 parts of the conductivity imparting agent (carbon black).
% By weight to 30% by weight is preferred. If it is less than 2% by weight, it does not serve as a conductive auxiliary. When added in an amount of 30% by weight or more, the function as a plasticizer is increased, and rubber elasticity is often impaired. About 5 to 15% by weight of the amount of the conductivity-imparting agent is the most well-balanced amount.

[0025]

EXAMPLES Hereinafter, specific Examples 1 to 6 and Comparative Examples 1 to 3 of the semiconductive resin composition according to the present invention and Example 7 as a production example of the present conductive roller will be described in detail. They do not limit the invention in any way. Table 1 lists the carbon blacks used.

[0026]

[Table 1]

(Semiconductive rubber layer 1) (A-1) 100 parts by weight of a terminal allylated oxypropylene-based polymer having a number average molecular weight Mn of 8000 and a molecular weight distribution of 2 (B) a polysiloxane-based curing agent (SiH value) 6.6 parts by weight of (0.36 mol / 100 g) (C) 10% isopropyl alcohol solution of chloroplatinic acid: 0.06 parts by weight and various carbon blacks shown in Table 1 in predetermined amounts are added and uniformly kneaded. After that, it is poured into the mold, 140
Approximately 3m by putting into an oven for 20 minutes and heating
m sheets were prepared. Then 3cm x 3cm on both sides
Were prepared from silver paste (prepared at five locations on one side), and the average volume resistivity and the variation at the five locations were measured by measuring the current value when 100 V DC was applied.

(Semiconductive rubber layer 2) Except that the semiconductive rubber layer 1 was mixed with 1 part by weight of DOP,
In the same manner, a sheet was prepared, and the average volume resistivity and its dispersion at five locations were measured. (Semiconductive rubber layer 3) (A-
In place of the component (1), a polyisobutylene polymer having a number average molecular weight Mn of 9000 and two terminal vinyl groups (A-
Except that 2) was used in a formulation using 100 parts by weight,
In the same manner, a sheet was prepared, and the average volume resistivity and its dispersion at five locations were measured. Table 2 shows the results of Examples 1 to 6 and Comparative Examples 1 to 3.

[0029]

[Table 2]

Example 7 Using the composition of Example 4,
A 15.8 mm roller was formed by coating on a SUS shaft having a diameter of 8 cm by liquid injection molding. The roller was attached to a developing roller portion of a micro line 400e (manufactured by Oki Data) to evaluate a solid black image. The Macbeth density of the 5,000th sheet was 1.35, which was good.

[0031]

By using the carbon black of the present invention, it is possible to obtain a stable semiconductive resin composition in which the variation among five places in the semiconductive region is within one digit. As apparent from Comparative Example 3, the DBP oil absorption was large,
When carbon black having a large iodine adsorption amount is used, even if an attempt is made to control the electric resistance in the semiconductive region, the dispersion becomes large. Further, the resistance can be stably controlled by adding the phthalate compound (Example 2). The semiconductive resin composition according to the second aspect of the present invention is a composition suitable for use as a semiconductive roller, and a good image can be obtained from a roller manufactured from the semiconductive resin composition.

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Claims (5)

[Claims] 1. A semi-conductive resin composition comprising, as a conductivity-imparting agent, carbon black having a DBP oil absorption of 100 ml / 100 g or less and an iodine adsorption of 25 mg / g or less. Conductive resin composition 2. The method according to claim 1, wherein the semiconductive resin composition has (A) at least one alkenyl group in a molecule,
A polymer in which a repeating unit constituting the main chain is an oxyalkylene unit or a saturated hydrocarbon unit. (B) a curing agent having two or more hydrosilyl groups in a molecule; and (C) a hydrosilylation catalyst. The semiconductive resin composition according to claim 1, wherein 3. The semiconductive resin composition according to claim 1, wherein the phthalic acid ester compound contains 2% to 30% by weight of the conductivity-imparting agent. 4. The molded article has a volume resistivity of 10 M (1
The semiconductive resin composition according to any one of claims 1 to 3, wherein the composition is in the range of 0 ⁷ ) Ωcm to 1 G (10 ⁹ ) Ωcm. 5. A semiconductive roller for use in an electrophotographic system using the semiconductive resin composition according to claim 1.